const Promise = require('bluebird');
const a = 'array';
const b = 'string';

function func (c, d, callback) {
  const array = [c];
  const number = c + d;
  console.log('number:' + number);
  array.push(number);
  return callback(null, array);
}


async function main(num1, num2) {
  const funcAsync = Promise.promisify(func);
  
  const arr = await funcAsync(num1, num2);
  console.log('arr:' + arr);
  
}

main(a,b);

